Rediffusion and British Relay Television were two of the big names. The latter had over a million subscribers in the late 1960s.
I think they were quite common in new towns and places that (because of geography) were not well served by broadcast transmitters. In Milton Keynes, for example, TV aerials were banned and all houses were cable-ready. Due to the number of people moving out from London, they also received the London ITV service as well as the local one.
You can still see evidence of the old systems in the areas served.
View attachment 73190
Image shows a photo of a concrete 'manhole' cover in situ, with 'Rediffusion' written on it.